Numerical control (Numerical Control; hereinafter, referred to as NC) apparatuses are apparatuses that cause a machine tool to machine a material (workpiece) in accordance with a machining program. Before machining by a machine tool is started, it is necessary to check that the machine tool operates without collisions between various components being caused. Therefore, an interference check simulation is performed in advance. In this interference check simulation, checks are made as to whether any of the components constituting the machine tool, a tool used in the machine tool, the material, and a jig interfere with each other. In order to perform such an interference check simulation, three-dimensional shapes of the tool and the like are necessary.
A method of performing an interference check includes a method in which the three-dimensional shapes of the components constituting the machine tool, tool, material, and jig are approximated as plane data groups. In this method, each plane data group is arranged at a position on the machine tool that operates in accordance with a machining program and it is detected whether collisions occur by calculating intersection lines by using a computer.
The three-dimensional shapes of the components constituting the machine tool do not change for each machining program; however, the three-dimensional shapes of the tool, material, and jig change for each machining program. Therefore, if the three-dimensional shapes of the tool, material, and jig can be prepared quickly, many machining programs can be executed. Moreover, collisions between components can be detected more accurately if the expression capability of a three-dimensional shape is higher.
Methods of inputting a three-dimensional shape into an NC apparatus, for example, include the following three methods:
(Method 1) Method of inputting a three-dimensional shape generated by three-dimensional CAD (Computer Aided Design).
(Method 2) Method of setting, as a three-dimensional shape, a shape that is generated by rotating a contour shape, which is obtained when a rotating body is projected onto the plane that passes through the rotation axis of the three-dimensional shape, about the center line of the contour shape.
(Method 3) Method of preparing a template that has dimension lines obtained by replacing dimension values expressing a shape by parameters and parametrically inputting a three-dimensional shape by inputting the parameters.
In the case of the method 1, it is necessary to prepare a PC and three-dimensional CAD software in addition to the NC apparatus; therefore, investment in equipment is required. Moreover, the NC apparatus in this case cannot change the input three-dimensional shapes.
In the case of the method 2, because a linear or arc contour shape can be specified by the NC apparatus, the workload is reduced compared with the method 1. Moreover, the NC apparatus in this case can change and reuse the input three-dimensional shapes.
In the case of the method 3, because a three-dimensional shape can be generated simply by inputting the parameters related to the template in the NC apparatus, the workload can be reduced compared with the method 2. Moreover, the NC apparatus in this case can also change and reuse the input three-dimensional shapes.
Meanwhile, regarding the expression capability of a three-dimensional shape, the method 2 is higher than the method 3 and the method 1 is higher than the method 2. However, regardless of which method is used, because an operator is involved, erroneous inputs can easily occur.
When an interference check simulation is performed, if the workload is low, the reusability of a three-dimensional shape is high, and the expression capability of a three-dimensional shape is high, this results in easy and accurate generation of a three-dimensional shape. Therefore, the method 2 is a useful method.
In the method 2 as described above, an operator faces the screen of the NC apparatus and manually inputs a cross-sectional shape obtained by projecting a tool onto the plane that passes through the rotation center of the tool shape. With this method 2, if the cross-sectional shape becomes complicated for generating a three-dimensional shape that closely resembles the actual tool, the number of times an input is manually made increases and therefore erroneous inputs by the operator may occur.
Thus, a system is used in some cases which generates a shape obtained by extracting a contour shape from an image captured by a camera and rotating the contour shape instead of the operator manually inputting a contour shape of a cross section. With the use of this system, a three-dimensional shape can be generated without involving the operator manually performing inputs. In such a system, for example, a three-dimensional shape is generated on the basis of a two-dimensional image obtained by imaging a rotating body (for example, see Patent Literature 1).